🥬 Lettuce How hard it is to control: ★★★☆☆ 3/5

Downy mildew of lettuce

Disease caused by an oomycete (fungal-like organism), particularly dangerous in cool, wet springs. Spreads rapidly in dense cultivation.

Symptom photos

Downy mildew of lettuce — Iceberg lettuce leaf — pale, angular patches and browning veins — Iceberg lettuce leaf — pale, angular patches and browning veins Photo: Rasbak, licence CC BY-SA 3.0

Symptoms

Yellow spots on leaves
Whitish coating on underside
Leaf browning

What it does to the crop

Complete loss of heads with severe infection
Bitter taste of leaves
No possibility of sale

What encourages it

Cool, humid weather
Dense cultivation
Poor ventilation

Prevention

Appropriate spacing
Tunnel ventilation
Resistant varieties

⚠️ Before you reach for a spray

This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.

Keep the disease atlas with you in the garden

In the app you can identify a disease from photos, work out the spray dose for your own bed and log the treatment in your task calendar. Free, no sign-up, works offline.

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